Apparatus for continuous foil production by vapor deposition



May 18,

H. R. SMITH, JR

APPARATUS FOR CONTINUOUS FOIL PRODUCTION BY VAPOR DEPOSITION FilOd June 5. 1962 FIG- l 4 Sheets-Sheet 1 Mussi Bc'r HTTOPA/IYJ H. R. SMITH, JR

4 Sheets-Sheet 2 APPARATUS FOR CONTINUOUS FOIL PRODUCTION BY VAPOR DEPOSITION May 18, 1965 Filed June 5, 1962 "I, I/ f" l" g 7l- FLMl/v'r Jz/PPLY Mam/fr A/ Powli (/7 .ig/nr INVENTOR. Hua/v 2 5w 7H. Je

May 18, 1965 H. R. SMITH, JR 3,183,563

APPARATUS FOR CONTINUOUS FOIL PRODUCTION BY VAPOR DEPOSITION Filed June 5, 1962 4 Sheets-Sheet 3 INVENTUR. HUGH 2.5M/ nm@ Arran/IK! May 18 1965 H. R. sMrrH. JR 3,183,563

APPARATUS FOR CONTINUOUS FOIL PRODUCTION BY VAPOR DEPOSITION Filed June 5. 1962 4 Sheets-Sheet 4 ENToR. Hui# .5M/rw, di, O

I TTQIA/FK United States Patent O 3,183,563 APPARATUS FOR CONTINUOUS FOIL PRODUC- TION BY VAPOR DEPOSITION Hugh R. Smith, Jr., Piedmont, Calif., aignor to T emescal Metallurgical Corporation, Berkeley, Calif., a corporation of California Filed June 5, 1962, Ser. No. 200,157 Claims. (Cl. 22-57.3)

The present invention relates to an improved apparatus for the continuous production of thin foils and also to an improved apparatus for the coating of foils or sheets of material with an adherent film.

The present invention provides for the vacuum deposition of materials such as metal for the production of foils or films. In particular, the invention relates to continuous production wherein a very substantial quantity of foil, for example, may be produced without vacuum difficulties and problems normally attendant high vacuum processing. Although it is well known that high vacuums may be established and maintained, even under adverse circumstances, by the utilization of suitable pumping speeds and appropriate vacuum techniques, it has quite commonly been considered that such applications are limited to laboratory utilization. The present invention provides for the practical application of high vacuums to the vapor deposition of materials for the production of very thin films which may be utilized as separate foils or alternatively may be employed in connection with the coating of foil or web material. Continuous high quantity and quality production with high vacuum processing is herein achieved by novel vacuum staging through which continuous foils or the like are fed. Such foils or the like are thus movable between atmospheric pressure and high vacuum processing regions without loss of vacuum in such regions.

Truly high quality vapor deposition may be accomplished in very high vacuum regions, wherein substantially free molecular flow is obtained so that no recombination of vaporized molecules occurs in the free flow regions. This provides for the deposition of a substantially molecular coating, i.e., one molecule at a time, so as to achieve maximized uniformity of the coating. There has been disclosed in my prior co-pending patent application, Serial Number 132,423, led in the United States Patent Otiice on August l, 1961, for Foil Production, a process and apparatus for producing thin foils. Such process utilizes the aforementioned high vacuum conditions and the present invention constitutes an improvement thereover in providing for a continuity of production through movement of the vapor deposited coating between high vacuum regions and substantially atmospheric conditions.

In accordance herewith, a vapor deposited coating is removed from a high vacuum coating region upon a rotatable drum extending between the vacuum and the atmosphere. Vacuum integrity is maintained by the separate evacuation of consecutive stages about the drum periphery to achieve a large pressure gradient along the path of the coating without applying stresses to the coating. In addition, the present invention provides for the vapor deposition of thin films upon a foil or web, either for the purpose of producing multilayer foils or, alternatively, for the coating of a thin backing material in predetermined arrangement, so as, for example, to produce writing thereon. The invention may, for example, be employed to deposit a thin film of metal in predetermined arrangement upon a strip or sheet of transparent backing of minimal thickness, so as to leave transparent portions thereof available for the viewing of materials subsequently packaged or encased in the coated backing material. The apparatus of this invention provides for continuous foil or coating production and additionally provides an 3,183,563 Patented May 18, 1965 improvement in the handling of the product to facilitate removal of same from high vacuum regions without damage.

Certain preferred embodiments of the present invention are illustrated in the accompanying drawings, wherein:

FIGURE 1 is a longitudinal sectional view taken in a central vertical plane through a foil furnace in accordance with the present invention;

FIGURE 2 is a transverse sectional view of the same furnace as illustrated in FIGURE l and taken in the plane 2 2 of FIGURE 1;

FIGURE 3 is a sectional view of a suitable electrongun heat source as employed in the invention hereof;

FIGURE 4 is a longitudinal sectional view taken in a central vertical plane through an alternative embodiment of the present invention adapted for the application of coating to a web or the like; and

FIGURE 5 is a sectional view taken in a central vertical plane of an alternative embodiment of the present invention including stencil means for limiting coating areas upon a substrate webbing or the like to be coated in the furnace illustrated.

Considering now a preferred embodiment of the present invention and referring to FIGURES 1 and 2, it is first briefly noted that the continuous foil furnace of the present invention provides a rotary drum as an important component therein. Coating material vaporized in a high vacuum chamber is deposited either upon this drum itself or upon materials carried by the drum. The drum is arranged in relation to walls defining the high vacuum chamber so as to rotate between the chamber and external atmosphere. A plurality of vacuum barriers or walls closely engage the drum at spaced intervals along the periphery thereof, and multistage pumping is provided for successively reducing the pressure between adjacent vapor barrier walls about the drum circumference. In this manner, vacuum integrity is maintained within the reaction chamber of the furnace hereof, while at the same time limiting vacuum sealing problems to that of sealing of the drum. Coating material applied as a film upon the drum, or alternatively as a film upon some backing member extending about the drum, thus need not be subjected to pressures and stresses otherwise involved in extending this film through vacuum locks. Continuous processing requires extension of the foil or the like from the evacuated reaction volume, in order that such foil may be available for use, and the drum arrangement of the present invention is highly advantageous in this respect.

In addition to the foregoing features of the present invention, there is also provided for the condensation of vaporized coating material upon a heated substrate. It has been found that the degree of adhesion of vapor deposited materials may be controlled by controlling substrate temperature upon which such materials are deposited. The rotating drum of the present invention is ideally suited to controlled heating in order to maintain the substrate within desired temperature ranges for improved control over certain characteristics of foil formation. Under those circumstances wherein it is desired to produce a separate foil by vapor deposition with the furnace hereof, it is highly advantageous for the foil to be readily separable from the substrate upon which it is deposited. Maintenance of the substrate within a particular temperature range minimizes adhesion between the deposited coating and the subtrate itself, even though extremely clean surfaces are employed and conditions are maintained which would indicate tight adhesion. Under alternative circumstances, wherein it is desired to vapor deposit a thin film of material upon a webbing or sheet in a high vacuum, the rotating drum hereof provides an ideal carrier for the film substrate, so that the latter may be maintained within a predetermined temperature range for maximized adhesion of the vapor deposited material to the substrate.

Considering now the present invention is somewhat greater detail and referring to FIGURES l and 2 of the drawing, there will be seen to be illustrated a vacuum enclosure 11 defined at least in part by walls 12. High speed pumping means, such as diffusion pumps 13, are connected to the interior of the chamber 11 through the walls 12, and backing pumping means 14 may be employed in connection with these diffusion pumps. Although alternative pumping means may be employed, it is herein briefly noted that quite high pumping speeds are required in order to maintain the pressure of the chamber 11 at a desired minimum amount, particularly during vacuum deposition of materials within this chamber.

Within the vacuum or reaction chamber 11 there is disposed a vapor source 16. This source is illustrated as comprising a crucible 17 containing molten material 18 for vapor deposition and an electron beam generator 19 producing an electron beam 21 directed onto the top of this molten metal for bombardment heating thereof. Viewing means 22 may be provided in extension through a wall of the housing 12 for direct visual observation of the interior thereof. It is possible to charge the crucible 17 with material 18 in a variety of ways, and there is shown a tundish or spout 26 directing molten material into the crucible 17 from a melting Crucible 27. Coating material 18 is provided to the furnace through a vacuum lock 28 extending through a wall of the furnace and the material is fed into the melting erucible 27 whereat the material is initially melted. This melting is shown to be accomplished by bombardment heating with one or more electron beams 29 directed into the Crucible from a source 31.

The coating material feed and vaporization system illustrated in FIGURE l and described above is advantageous in providing for initial melting of the material at a distance from the location of vapor deposition. Purification of the coating material fed into the vacuum chamber may thus be accomplished in the melting Crucible 27 by driving volatile impurities therefrom at a distance from the location of vapor deposition. The coating material may be initially provided through the vacuum lock 28 in any desired form. such as for example, solid pieces of scrap metal which are successively dumped into the melting crucible 27 by suitable feed means herein considered to be included in the illustrated vacuum lock means 28.

Continuous foil production is attained by the utilization of a movable substrate upon which coating material is vapor deposited. This moving substrate is formed as a drum 41 rotatably mounted by a shaft 42 above the vapor generator 16. Drive means, such as an electric motor 43, is coupled to the drum shaft 42 and preferably located exteriorly of the vacuum chamber 1l, as illustrated in FIGURE 2. Within the drum 4l, there may be provided cooling means schematically illustrated in FIG- URE l as cooling pipes 44. These cooling means serve to prevent overheating of bearing surfaces, for example, and may also be employed to control drum surface temperature, as noted in greater detail below.

Vacuum sealing means are provided about the drum 41 to maintain vacuum integrity within the chamber 11, and at the ends of the drum these sealing means may take any conventional form desired. inasmuch as the drum is located to rotate between atmospheric conditions exteriorly of the furnace and high vacuum conditions interiorly thereof, special provision is made for providing vacuum sealing about the drum circumference. This vacuum sealing is accomplished by the provision of a plurality of vacuum stages displaced circumferentially about the drum. These individual stages are defined by separate walls l, 52, 53, and 54, which may be disposed in generally parallel spaced relationship in extension from the side walls of the chamber into close engagement with both sides Gil 4 of the drum periphery. Intermediate vacuum chambers 56, 57, and 58 are defined between the walls 5l to 54, and cach of these intermediate chambers are connected to vacuum pumping means, such as schematically illustrated at 6l, 62, and 63. The walls 51 to 54 extend into very close engagement with the periphery of the drum 41, and there may be provided resiliently mounted rollers 64 at the inner ends of each of the walls substantially engaging the drum itself. Under those circumstances wherein a coating of substantial thickness is to be vapor deposited upon the drum for subsequent removal therefrom as a thick foil, it is apparent that the total drum radius is substantially greater on the side leaving the chamber 11 than on the entering side. Under such circumstance, it is advisable to provide for adjustable wall ends, however, under most circumstances and with suitable pumping speeds available to evacuate the chambers 56, 57, and 58, it is not necessary to adjust the spacing between the inner ends of the walls and the drum periphery.

The vapor generator 16 serves as a source of vapor of material to be formed into a foil or the like, and as indicated in FIGURE l, this vapor rises from the upper surface of the molten material 18 within the Crucible 17 and to condense upon the relatively cool drum surface above the Crucible. Rotation of the drum provides for vapor condensation upon a continuously replaced substrate, i.e., the drum surface, and this continuous coating is removed from the area of deposition by drum rotation. The coating material is carried on the drum from the vacuum chamber 11 through the intermediate vacuum chambers or stages to the exterior of the furnace. Outside of the furnace the vacuum deposited material or coating 71 upon the drum is separated from the drum as a foil. This removal may be accomplished by the disposition of a knife edge element 72 bearing against the drum periphery and directed toward the coated surface of the drum as it moves past the knife edge. As illustrated, a freely rotatable roller 73 is disposed adjacent the location of coating removal so that the vapor deposited material in the form of a foil then passes over this roller after removal from the drum. The foil 71 may then, for example, be wound about a take-up reel 74 over suitable intermediate rollers or the like, as indicated.

A variety of different beam generation means may be employed in the continuous foil production plant hereof, and there is illustrated in FIGURE 3 an exemplary electron beam source suitable for use herein. Referring to FIGURE 3, the source 19 is seen to include an electron emissive filament 81 disposed within a backing electrode 82 and electrically connected to a filament supply 83 for passing a current through the filament to raise the temperature of the filament to that of electron emission. Outside of the backing electrode 82 there is disposed an accelerating electrode 84 which is maintained at a positive potential with respect to the filament by an accelerating voltage supply 86. The electrons emitted from the filament 81 are attracted from the backing electrode in the form of a beam by the potential existing between the accelerating electrode 84 and filament 81. This electron beam 21 is shown to be initially directed generally upward from the electron source, and the beam is curved by the establishment of a magnetic tield passing transversely through the beam trajectory. This magnetic field may be established between magnet pole pieces 87 by energization of a magnet coil 88 therebetween from a magnet power supply 89. In passing through the magnetic field, which extends perpendicularly to the plane of FIG- URE 3, the electron beam 21 is curved, somewhat as indicated, to thus traverse an arcuate path and to impinge upon the upper surface of material 18 within the Crucible 17. The electron beam generator, briefly described above, is similar to one disclosed in a co-pending patent application of Charles W. Hanks, now Patent No. 3,177,535, however, the foregoing description is believed sufiicient to indicate one suitable type of generator. Of course, other types of electron beam generators may also be employed, however, it is highly advantageous to dispose such generators in positions which are protected from vapors and ions within the chamber. The generator 19 will be seen to be disposed below the top of the crucible 17` so that vapor arising from the molten material 18 within the crucible will generally travel away from the generator and not deposit thereon. Remotely disposed electron beam generators may also be employed, preferably with provision for limiting ion bombardment of thc electron emissivc filament.

Electron beams generated by sources such as illustrated in FIGURE 3 may be employed to initially melt material fed into crucible 27 and to vaporize material in the vapor source 16. ln addition, the present invention also provides for heating of the rotating drum 41. This may be quite readily accomplished by electron bombardment of the surface of the drum immediately ahead of the area upon which vapor deposits. A beam generator 77, such as described above, bombards the drum which is formed of a metal such as stainless steel to readily withstand heating.

Considering operation of the embodiment of the present invention described above, there is tirst established a very substantial vacuum within the chamber 11, by operation of the pumps 13 and 14. Additionally, the pumps 61, 62, and 63, are operated to maintain intermediate degrees of vacuum in the vacuum stages 56, 57, and 58, spaced about the drum periphery. As an example of operation wherein copper foil is to be formed, the internal atmosphere of chamber 11 was maintained at a pressure of 0.02 micron of mercury. With atmospheric pressure exteriorly of the foil production plant, the first vacuum stage 56 was maintained at 0.1 atmosphere` the next stage 57 was maintained at 0.01 atmosphere, and the third stage 58 was maintained at a pressure of -4 atmospheres. Copper scrap was placed in the lock 28 and fed therefrom into the purification crucible 27. With the electron beam generator 31 operating, this copper scrap was heated and melted within the purication crucible with a consequent volatilization therefrom of such impurities within the scrap as readily volatilize at melting temperature of copper. With the purification crucible 27 substantially full, molten copper tiowed down a tundish 26 into the vapor source crucible 17. Molten copper 18 within this crucible 17 was then further heated by electron beam bombardment to raise the temperature of the copper to that of vaporization. The drum 41 was rotated by the motor 43 at a peripheral velocity in the range of 80'to 250 feet per minute. The

drum was formed with a diameter of six feet so that this f did not require an undue rotational velocity of the drum.

1t has been determined that adherence of vapordeposited material to a moving substrate may be limited by controlling the temperature of the substrate. In the instance wherein copper foil, for example, was formed, it was desired for the vapor deposited material to be readily separable from the drum surface. Control over the temperature of the surface of the drum 41 was obtained by heating this surface, as for example, by electron beam bombardment from the source 77, and by providing for cooling of the drum interiorly thereof through the coolingtubes 44. Still considering the example of copper foil production, the drum was heated to a temperature in the range of 275 degrees Fahrenheit to 310 degrees Fahrenheit by electron beam bombardment. By heating the drum surface immediately before such surface passes into the area of vapor deposition, it was possible to quite accurately control the temperature of the substrate upon which the vapor deposited. With the drum rotating and the copper within the crucible 17 heated to vaporization, copper vapor rose from the crucible to deposit upon the moving drum surface. This deposition then formed a coating 71 upon the drum, and continued rotation of the drum moved the vapor deposited coating from the chamber 11 through the successive vacuum ,stages 58, 57, and 56, to the exterior of the housing. Outside of the chamber 11 and in atmospheric pressure, the knife edge 72 engaged the drurn to separate the coating 71 from the drum. This coating 7l, then in the form of a foil or thin sheet of copper, was drawn upon a take-up rccl or the like 74 through intermediate rollers directing thc foil onto thc take-up rcel.

A truly continuous foil production is accomplished by the present invention, inasmuch as the drum 4l continues to rotate and, with the maintenance of molten material within the vapor source` there is established a continuous vapor deposition upon the moving drum surface. 1n this manner it is possible to form extremely large areas of foil without a break therein. Control over the thickness of the foil is readily accomplished by controlling the rate of rotation of the drum, and, of course, the rate of vaporization of the copper is also controllable by controlling the amount of heat applied thereto. Preferably the rate of vaporization is maintained substantially constant, however, inasmuch as undue boiling ofthe copper may result in spattering of molten copper from the crucible. Separation of the vapor source and drum is also variable, however, it has been found in practical applications that a distance of 6 inches to 18 inches is desirable in this respect. Too great a separation of vapor source and drum or moving substrate will result in loss of a relatively large amount of the vapor which would then plate other portions of the interior of the furnace.

As regards the type of coating deposited herein, it will be appreciated that the very high vacuum established and maintained within the chamber 11 throughout vapor deposition provides ideal conditions for a substantially molecular vapor deposition. Very little, if any, recombination of vaporized molecules occurs prior to deposition of such molecules upon the substrate. As vapor molecules leave the top surface of the molten copper or other material within the crucible 17, they travel in substantially straight lines, inasmuch as the high vacuum minimizes the number of gas molecules aavilable for collision with the vapor molecules. An extremely fine coating upon the drum surface is thus attained, and it is possible to produce extremely thin foils or films in this manner. In common with the continuous foil production process and apparatus of my prior co-pending patent application Serial No. 132,423, filed in the U.S. Patent Oice on August 1, 1961, the invention hereof minimizes the difficulties of forming very thin foils. In distinction to other types of foil production wherein thick sheets of material are reduced in thickness to produce foil. The present invention builds the foil from zero thickness, and consequently, the production of extremely thin foils requires no more effort or expense than the production of thicker foils.

The present invention, as described above, is highly advantageous in providing a simplified and improved manner of removing vapor deposited material from a highly evacuated chamber within which deposition is carried out. The rotating drum 41 is highly advantageous in continuous foil production, for the drum itself extends between the vacuum chamber and atmospheric conditions exteriorly thereof. The plurality of intermediate vacuum stages about the drum periphery make it possible to maintain the high vacuum within the chamber while yet passing the vapor deposited coating therefrom. With a drum 41 having a diameter of about six feet and the length of about five feet, the opening between the atmosphere and the tirst vacuum stage 56 may be limited to about onehalf square inch. This limitation is quite practical in actual constructed apparatus and similar spacing may be employed between successive vacuum stages. With such a limitation upon the total communicating area between separate vacuum stages, conventional vacuum pumping means are suitable to maintain thepressure differentials identified in the example above. 1t is particularly noted that the high vacuum, as of the order of 0.02 micron of mercury, within the chamber 11 is not only initially established therein, but furthermore, is maintained therein throughout vapor deposition. This vacuum is maintained despite the fact that a substantial amount of gas may be evolved from the purification Crucible and, furthermore, that a certain amount of vapor is distributed throughout the chamber. Quite high speed pumping means are required to maintain this low pressure, however, conventional pumping means are suited therefor.

The crucibles 17 and 27 within the vacuum chamber 11 may be formed, for example, of graphite under the conditions wherein relatively low temperature metals such as copper are being vapor deposited upon the drum. With copper being employed as the deposited material, the drum may, for example, be formed of stainless steel although many other metals have also been found suitable. Substantially any desired foil surface may be produced by employing an appropriate substrate surface. Thus, for example, if it is desired to obtain a matte foil surface, it is only necessary to roughen the surface of the drum. An extremely smooth foil surface may be obtained by employing a very smooth drum surface. Under those conditions wherein a very high temperature material is to be vapor deposited it may be necessary to provide cooling for the crucibles, and in this case water cooled copper crucibles have been found to be advantageous.

The foregoing example, wherein operation of the invention as described in connection with the production of copper foil. is in no way limiting upon the invention hereof, for a wide variety of materials may be operated upon in accordance with this invention. Thus, for example, the continuous foil plant of the present invention is admirably suited to the production of very thin tantalum foil which finds wide applicability in the manufacture of electrical capacitors. Inasmuch as the drum cools rather rapidly, it will be appreciated that the vapor deposited material is relatively cool at the point of separation from the drum outside of the vacuum chamber. As above noted, the continuous foil production plant is adapted to the production of extremely thin foil as well as foils of greater thickness. Particularly in those instances wherein very thin foil is produced, the passage of this foil through the separate vacuum stages while yet attached to the roltating drum is highly desirable, inasmuch as no stress or strain is then applied to the foil. By leaving the foil upon the rotating drum as it passes out of the vacuum chamber into atmospheric conditions, it is possible to quite properly and readily seal the evacuated chamber without depending upon any structural qualities of the foil itself. The advantage of this will become readily apparent when it is considered that copper foil having a thickness of a few mils, for example, may be quite readily broken or damaged by undue pressure thereon as may be required in alternative structures wherein the foil alone is withdrawn from the vacuum chamber.

Although the present invention has been described above in connection with the production of continuous foil, it is in no way limited to applications wherein the foil is utilized alone. There are many circumstances calling for layered foils or very thin coatings of metal, for example, upon thin sheets of backing material. This circumstance is found, for example, in the production of electrical capacitors, wherein it is desired to produce very thin sheets having a high conductivity on one side and insulating properties on the other. One embodiment of the present invention adapted to produce thin coatings upon a web or sheet of backing material is illustrated in FIGURE 4. Referring to this figure, there will be seen to be shown a housing 101 defining a vacuum chamber 102 evacuated through suitable outlets 103 and connected to appropriate pumping means not shown. In this embodiment of the invention, there is also provided a drum 104 which is mounted for rotation in a position to dispose a part of the periphery of the drum within the chamber 102 and a part of the periphery entirely without the A flexible sheet or web 111 to be coated with a thin layer of vapor deposited material is supplied from a supply reel 112 over suitable rollers 113 to pass about the drum 104, through the chamber 102, and back out of the chamber onto a take-up reel 114. Rather than directly depositing material upon the web as it passes about the drum 104, there is shown in FIGURE 4 the provision of a separate or secondary drum 116 mounted for rotation within the chamber 102. The web 111 extends about one side of the drum 104 and thence about the drum 116 and back up about the primary drum 104 out of the vacuum chamber. A pair of guide rollers 117 and 118, preferably mounted for lateral movement under control of an operator exteriorly of the vacuum chamber, engage the web between the primary and secondary drums so as to thereby provide for appropriate tension upon the web passing through the vacuum chamber. A suitable vapor source 121 is provided beneath the secondary roller 116 and may, for example, include a crucible 122 and one or more electron beam generators 123 bombarding molten material 124 within the crucible. Various types of material feed means may be employed to initially or` continuously charge the Crucible 122 with the material 124 for vapor deposition.

In operation of this furnace, the take-up reel 114 is driven, as for example by a suitable motor 126, to withdraw the web 111 from the supply reel 112 and pass it through the vacuum chamber 102. With both of the drums 104 and 116 being mounted for rotation they will thus rotate as the web passes thereover. As the web is drawn through the vacuum chamber 102, vapor rising from the vapor generator 121 will be deposited upon the web in the very high vacuum maintained within the vacuum chamber. In distinction to the embodiment of the invention illustrated in FIGURE 1, it is normally desired herein for the vacuum deposited material to tightly adhere to the backing or web. This tight adherence commonly results from vapor deposition upon a clean surface` how` ever, for certain materials adhesion may be improved by controlled heating of the web. Under any conditions wherein heating of the web or the like is employed, care should be exercised not to damage the web. Only a relatively small amount of heat is applied to the primary and secondary drums of this furnace by the vapor deposited material, and consequently, it is normally not necessary to employ extensive cooling means for these drums. In particular, the upper drum 104 is well removed from any source of heat and the substantial travel of the vapor deposited material from the secondary drum to the primary one generally precludes overheating of this upper drum. Even the secondary drum 116, about which the web extends during vapor deposition of metal or the like onto the web. is not normally excessively heated, however, in many applications it may be desirable to employ some type of internal cooling for this drum. Lateral movement of the guide rollers 117 and 118 is highly advantageous in providing for precise adjustment of web tension, and this control over web tension is made possible by the utilization of both primary and secondary drums, as illustrated.

About the take-up reel 114 there is then wound a web having a tightly adherent coating of vapor deposited material. T is coating may, for example, have a thickness of a ew mi and may comprise any of a wide variety of metals or other types of material. In particular, it is noted that utilization of a web having electricall 'n- Sulating Propertissaasihesm E El conBtEiii-gietal such as cir-perd sheet of composite or coated materia tageous for use in the manufacture of electrical capacitors. By the appropriate choice of backing material or web material 111 and coating material 124, it is possible to produce a wide variety of coated foil. No limitation is intended bythe examples of operation provided herein, for quite clearly metal ma be coated on metal, metal rnay be coal'ltLQQgQnnlmn/frnegat'tcoated on metals. "r------c In addition to the above-noted applications of the present invention and such other applications as may be readily apparent rto those skilled in the art, particular attention is invited to the applicability of this invention for producing such as commercial wrapping materials. An alternative embodiment of the present invention particularly adapted to such usage is illustrated in FIG- URE 5. wherein there is employed two rotatable drums 201 and 202 extending between the interior of a highly evacuated chamber 203 and the atmosphere. A housing 204 defines the vacuum chamber 203, and evacuation piping 206 extends from this housing for connection to suitable high speed pumping means to maintain a very high vacuum within the chamber. In this example of the invention, material is vacuum deposited upon a exible substrate such as a sheet 207 which is fed into the vacuum chamber 203 about one of the sealing drums 201 and out of the vacuum chamber about the second sealing drum 202. In common with the above described embodiments of the present invention, each of the drums 201 and 202 have a plurality of intermediate vacuum stages communicating with the periphery of each drum along both sides thereof, and each of these stages are independently evacuated, as indicated by the arrows in FIGURE 5, to thereby maintain intermediate vacuum conditions in each of the stages. With the walls defining these stages coming into very close proximity with the periphery of the drum, it is then possible to maintain the desired high vacuum within the chamber 203 while yet passing the sheet 207, for example, from atmospheric conditions into the chamber. As illustrated, the sheet 207 is fed from a supply reel 211 into the chamber 203 about the drum 201 and thence over a roller 212 and around a rotating drum 213. It -is while passing about this drum 213 that a coating is vacuum deposited upon the moving sheet 207. This sheet then extends about a further roller 214 and about one side of the sealing drum 202 out of -the vacuum chamber and about a take-up reel 216. Beneath the interior drum 213 there is disposed a vapor generator 217 which, may for example, be formed in the manner described above and includes means containing a molten pool of material to be deposited and means applying heat to such a pool for vaporization ofthe coating material.

In the manufacture of partially coated foils or sheets, for example, there is provided in accordance herewith for the passage of a second or stencil sheet 221 through the vacuum chamber 203. This stencil sheet 221 may be formed of any suitable material such as a thin foil of metal or a thin sheet of plastic or the like. The stencil sheet 221 is provided with desired cutouts Corresponding to the areas of desired vapor deposition upon the sheet 207. Furthermore, the stencil sheet 221, which may be one continuous member or belt, is fed into the vacuum chamber 203 about a guide roller 222 onto the sheet 207 thence through the intermediate vacuum chambers about the periphery of sealing drum 201. Consequently, as the sheet 207 passes into the vacuum chamber 203 it is covered on its lower surface by the stencil sheet 221. This stencil sheet then extends about the roller 212 and about the rotating drum 213. As the sheet 207 passes over the vapor generator 217, it will .thus be seen to be covered by the stencil sheet 221 so .that vapor deposits upon both the stencil sheet and upon the backing sheet only through cutout portions of the stencil sheet. This composite sheeting then passes over the guide roller 214 and out of the vacuum chamber 203 about the sealing drum 202. Exteriorly of the housing 204 the stencil sheet 221 is withdrawn from the sheet 207 by passage about a roller 223, so that the sheet 207 as it is wound upon the take-up reel 216 is only coated upon those areas of the sheet which were exposed by openings in the stencil sheet. Suitable drive means may -be connected to the take-up reel 216 in order to move the sheet 207 through the vacuum chamber, and likewise separate drive means may be provided for the stencil sheet, or alternatively it may be sufficiently pressed against the sheet 207 as to travel therewith through the vacuum chamber.

Inasmuch as a certain amount of coating material is deposited upon the stencil sheet, it is desirable to remove this material therefrom and such is readily accomplished lby the utilization of an endless stencil sheet passing through a recovery unit 226, wherein this coating material may be removed from the stencil sheet. Recovery of the coating material from the stencil sheet in the unit 226 may be accomplished in a variety of ways, de-

pending upon the nature of the' separation process required. Thus, for example, there may be employed a chemical cleaning of the stencil sheet or alternatively it may only be necessary to heat the stencil sheet in passage through the unit 226 in order to melt off the material coated thereon. This recovered coating material may then be again employed in the vapor generator 217, so that no loss of coating material occurs through the utilization of the stencil sheet.

A wide variety of applications of partially coated backing sheets is possible. It is thus possible, for example, to produce partially transparent wrapping for commercial items such as bread or the like. By the provision of appropriate openings in the stencil sheet, it is possible to apply writing, pictures, fanciful illustrations and the like to the backing sheet 207 that may in turn be transparent. The ability of the present invention to deposit extreme-ly thin and uniform coatings of metal, for example, clearly commends the apparatus to this type of production. An almost monoatomic layer of coating material may be applied in accordance with the present invention, and thus vacuum deposition of metals or the like becomes widely applicable. This ability to deposit such a thin coating in a uniform manner then makes the utilization of the present invention highly advantageous from an economic view point, not only in those fields where vacuum deposition is presently practiced, but furthermore, in many additional fields such as the one suggested above.

Vacuum deposition of materials such as metal in the very high vacuum employed -in the plant of this invention results in a uniformity of coating hitherto unavailable. Vapor molecules from the vapor generator travel in substantially straight lines into impingemen't with a substrate to be coated, and the almost total absence of gas molecules in the path of vapor -travel minimizes molecular collisions and agglomeration of vapor molecules. Consequently, these molecules of vapor are deposited almost individually upon the substrate, so that there is thus attained an extremely uniform coating. Thus, even though the coating produced hereby may be maintained extremely thin, it yet entirely covers the substrate without porosity or irregularity normally encountered in coating operations. In this manner then, it is possible to apply a much thinner coating and yet obtain a full and complete coverage of the article coated.

In all of the embodiments of the invention described above, it will be seen that particular provision is made for movement of the coating from the high vacuum cham- -ber wherein the coating is accomplished. This is particularly important when very thin coatings are employed, for most certainly such coatings have almost no structural strength of their own. By the utilization of rotating drums with a plurality of intermediate vacuum stages about the periphery thereof, the present invention provides for ready movement of very thin foils or coatings from highly evacuated volumes to atmospheric pressure without endangering the high vacuum of the chamber.

There has been described above various embodiments of the present invention, however, these embodiments are set forth as illustrative only, and it is not intended to limit the invention by the exemplary showings. Refer ence is made to the appended claims for a precise delineation of the true scope of this invention.

What is claimed is:

1. An apparatus for the continuous manufacture of a thin foil comprising, a housing defining a main vacuum chamber, a rotatable drum mounted in said housing so that the periphery of said drum forms a portion of a wall of said chamber, a plurality of vacuum sealing chambers disposed about the periphery of said drum immedi` ately outside said housing, means to'evacuate said main vacuum chamber to a high vacuum and means to evacuate said sealing chambers to provide progressively increased vacuum to the surface of said drum as said surface approaches said main vacuum chamber, a crucible within said chamber for receiving material to be vaporized,` first electron beam heating means within Said chamber adjacent said crucible for vaporizing the material in said crucible, said rst electron beam heating means including focusing means for focusing the electron beam onto the surface of the material in said crucible for vaporization thereof, and second electron beam heating means within said chamber adjacent said drum, said second electron beam heating means including focusing means for focusing the electron beam onto the surface of said drum for heating the surface of the drum to control adhesion of the coating thereto.

2. An apparatus for the continuous manufacture of a thin foil comprising, a housing defining a main vacuum chamber, a rotatable drum mountedin said housing so that the periphery of said drum forms a portion of a wall of said chamber, a plurality of vacuum sealing chambers disposed about the periphery of said drum immediately outside said housing, means to evacuate said main vacuum chamber to a high vacuum and means to evacuate said sealing chambers to provide progressively increased vacuum to the surface of said drum as said surface approaches said main vacuum chamber, a crucible within said chamber for receiving coating material to be vaporized, first electron beam heating means within said chamber adjacent said crucible for vaporizing lthe material in said crucible, said electron beam heating means being positioned so that the electron beam is generated at a point below the level of the material in said crucible, said rst electron beam heating means including focusing means for focusing the electron beam in a generally arcuate path onto the surface of the material in said crucible for vaporization thereof second electron beam heating means within said chamber adjacent said drum, said second electron beam heating means for focusing the electron beam onto the surface of said drum for heating the surface of said drum prior to the deposition of the coating material thereon in order to control the adhesion of the coating to the surface of the drum, means for cooling the interior of said drum to further control the adhesion of the coating to the surface of the drum, and means for removing the coating directly from the surface of the drum exteriorly of said chamber in the form of a continuous unsupported foil web.

3. An apparatus for the continuous manufacture of a thin foil comprising, a housing defining a main vacuum chamber, a rotatable drum mounted in said housing so that the periphery of said drum forms a portion of a wall of said chamber, a plurality of vacuum sealing chambers disposed about the periphery of said drum immediately outside said housing, means to evacuate said main vacuum chamber -to a high vacuum and means to evacuate said sealing chambers to provide progressively increased vacuum to the surface of said drum as said surface approaches said main vacuum chamber, a vaporizing crucible within said chamber for receiving coating material to be vaporized, first electron beam heating means within said chamber adjacent said crucible for vaporizing the material in said crucible, said electron beam heating means being positioned so -that the electron beam is generated at a point below the level of the material in said crucible, said first electron beam heating means including magnetic focusing means for focusing the electron beam in a generally arcuate path onto the surface of the material in said crucible for vaporization thereof, second electron beam heating means within said chamber adjacent said drum, said second electron beam heating means including focusing means for focusing the electron beam onto the surface of said drum for heating the surface of said drum prior to the deposition of the coating material thereon in order to control the adhesion of the coating to the surface of the drum, means for cooling the interior of said drum to further control the adhesion of the coating to the surface of the drum, a melting crucible within said chamber, vacuum lock means for introducing solid coating material to be vaporized into said melting crucible' without destroying the vacuum in the main vacuum chamber, third electron beam heating means within said chamber for melting and purifying the coating material in said melting crucible, means for controlling said third electron beam heating means so that the coating material in said melting crucible is maintained in molten form without vaporization thereof, means for transferring the molten coating material from said melting crucible to said vaporizing crucible, and means for removing the coating directly from the surface of the drum exteriorly of said chamber in the form of a continuous unsupported foil web.

4. An apparatus for the continuous manufacture of a thin foil comprising, a housing defining a main chamber, a rotatable drum mounted in said housing so that the periphery of said drum forms a portion of a wall of said chamber, a plurality of vacuum sealing chambers disposed about the periphery of said drum immediately outside said housing, means to evacuate said main vacuum chamber to a high vacuum and means to evacuate said sealing chambers to provide progressively increased vacuum to the surface of said drum as said surface approaches said main vacuum chamber, a crucible within said chamber for receiving coating material to be vaporized, first electron beam heating means within said chamber adjacent said crucible for vaporizing the material in said crucible, said first electron beam heating means including focusing means for focusing the electron beam onto the surface of the material in said crucible for vaporization thereof, second electron beam heating means within said chamber adjacent said drum, said second electron beam heating means including focusing means for focusing the electron beam onto the surface of said drum for heating the surface of said drum prior to the deposition of the coating material thereon in order to control the adhesion of the coating to the surface of the drum, and means for removing the coating directly from the surface of the drum in the form of a continuous unsupported foil web.

5. An apparatus for the continuous manufacture of a thin foil comprising, a housing defninga main chamber, a rotatable drum moun-ted in said housing so that the periphery of said drum forms a portion of a wall of said chamber, a plurality of vacuum sealing chambers disposed about the periphery of said drum immediately outside said housing, means to evacuate said main vacuum 13 chamber to a high vacuum and means to evacuate said sealing chambers to provide progressively increased vacuum to the surface of said drum as said surface approaches said main vacuum chamber, a Crucible within said chamber for receiving coating material to be vaporized, first electron beam heating means within said chamber adjacent said crucible for vaporizing the material in said crucible, said first electron beam heating means including focusing means for focusing the electron beam onto the surface of the material in said Crucible for vaporization thereof, second electron beam heating means within said chamber adjacent said drum, said second electron beam heating means including focusing means for focusing the electron beam onto the surface of said drum for heating the surface of said dmm prior to the deposition of the coating material thereon in order to control the adhesion of the coating to the surface of the drum, and means for removing the coating directly from the surface of the drum in the form of a continuous unsupported foil web.

References Cited by the Examiner UNITED STATES PATENTS MICHAEL V. BRINDISI, Primary Examiner.

WILLIAM J. STEPHENSON, Examiner. 

4. AN APPARATUS FOR THE CONTINUOUS MANUFACTURE OF A THIN FOIL COMPRISING, A HOUSING DEFINING A MAIN CHAMBER, A ROTATABLE DRUM MOUNTED IN SAID HOUSING SO THAT THE PERIPHERY OF SAID DRUM FORMS A PORTION OF A WALL OF SAID CHAMBER, A PLURALITY OF VACUUM SEALING CHAMBERS DISPOSED ABOUT THE PERIPHERY OF SAID DRUM IMMEDIATELY OUTSIDE SAID HOUSING, MEANS TO EVACUATE SAID MAIN VACUUM CHAMBER TO A HIGH VACUUM AND MEANS TO EVACUATE SAID SEALING CHAMBERS TO PROVIDE PROGRESSIVELY INCREASED VACUUM TO THE SURFACE OF SAID DRUM AS SAID SURFACE APPROACHES SAID MAIN VACUUM CHAMBER, A CRUCIBLE WITHIN SAID CHAMBER FOR RECEIVING COATING MATERIAL TO BE VAPORIZED, FIRST ELECTRON BEAM HEATING MEANS WITHIN SAID CHAMBER ADJACENT SAID CRUCIBLE FOR VAPORIZING THE MATERIAL IN SAID CRUCIBLE, SAID 